What is significant about the first crusade?

Christian knights reclaimed Jerusalem in the first crusade after seven weeks of siege. They waged a religious war in which they massacred both the Muslim and Jewish population who controlled the Holy City.

In 1095, armies of Christians from Western Europe answered a plea from Pope Urban II. He asked the armies to wage war against the Muslim forces who controlled the Holy Land. The earliest crusaders were mere French and German peasants, who were replaced by thousands of Christian soldiers. In June 1099, the Christian armies arrived in Jerusalem where they found the walls of the city heavily fortified. The soldiers built towers and fought their way over the walls. They entered the city, opening the Gate of Saint Stephen which allowed the foot soldiers to enter and capture Jerusalem. This led to the formation of a number of Latin Christian states. The Muslims who remained in the area vowed to wage holy war, jihad, with the intent of regain control of the area.